Thermographic developing apparatus



June 10, 1969 R. c. GOQDMAN ETAL 3,449,547

THERMOGRAPHIC DEVELOPING APPARATUS Filed Dec. 27, 1966 INVENTORS Robert C. Goodman Robert L. Boston United States Patent 3,449,547 THERMOGRAPHIC DEVELOPING APPARATUS Robert C. Goodman, Binghamton, and Robert L. Boston, Vestal, N.Y., assignors to GAF Corporation, New York, N.Y., a corporation of Delaware Filed Dec'. 27, 1966, Ser. No. 604,722 Int. Cl. H05b 1/02 US. Cl. 219-216 1 Claim ABSTRACT OF THE DISCLOSURE completed.

This invention relates to photocopying apparatus and, more particularly, to improvements in the developing segment of the device for processing and developing diazo-type copying materials.

Apparatus for processing diazo-type materials are widely known and used in industry. Generally, an apparatus of this type utilizes three basic processing segments or assemblies combined into a single complete operating unit. The first segment pertains to the printer segment of the apparatus wherein sensitized material, in contact with an original to be copied, is exposed to high intensity light. Subsequently, in the second segment or assembly of the apparatus, commonly designated as the separator-conveyor unit, the exposed sensitized material is separated from the original. The original may be delivered at a predetermined location into a suitable receiving tray, whereas the exposed sensitized material is conveyed to the third segment of the apparatus, generally designated as the developer. In the developer the exposed sensitized material is subjected to the vapors of a volatile developing agent, as for example, 'heated aqueous ammonia, and thereafter delivered into a print delivery receiving tray.

Recently, the developing processes have been improved with regard to specific types of idazo materials which no longer require the application of either fluid or vaporized developing agents. These materials, frequently designated as thermodiazo materials include chemical substances which, upon application of heat, liberate either ammonia or other alkaline agents which will effect the development of the previously exposed original copy sheet.

The developing portions of the photocopying device heretofore utilized in the developing of the so-called thermodiazo materials have employed rotating heated cylinders generally constituted of a heat-resistant vitreous, glass or metallic material over the surface which the exposed sensitized material is moved by means of moving conveyor belts. Although these developers have proven satisfactory during commercial operation, the need for numerous rotating and moving parts has rendered the complex construction thereof expensive and difiicult to maintain.

The present-invention overcomes the foregoing and other disadvantages by providing an improved developing apparatus for developing diazo-type materials with heat utilizing an advantageous construction having a minimum of moving components. One of the major features of this invention lies in the use of a stationary heated low-friction platen in lieu of the rotating cylinder, along or past which the exposed sensitized material moves over a guiding member spaced in proximity to the platen. Simple and inexpensive rollers are employed in feeding the materials to the developer and removing it therefrom.

It is accordingly a primary object of this invention to provide an improved heating apparatus of simple and inexpensive construction for the development of thermodiazo materials.

A further object of this invention is to provide a simplified apparatus for moving exposed sensitized thermodiazo materials through the developing section of a photocopying device.

A more particular object of this invention is to. provide a stationary platen member heated to an optimum temperature range and contacted by thermodiazo materials moving at a predetermined rate of speed along the surface of the platen.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view, partially in schematic section, of one embodiment of the apparatus for developing diazo-type materials according to this invention;

FIG. 2 is an elevational sectional view, partially in schematic, of a second embodiment of the developing apparatus according to this invention; and

FIG. 3 is an elevational sectional view, partially in schematic, of a third embodiment of the developing 'apparatus according to this invention.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a pair of end frames 10, only one of which is illustrated, the other having been deleted to permit viewing of the internal mechanism.

A platen 11 of somewhat dish-shape cross-section is positioned between and fastened to end frames 10 through suitable fastening means, not shown. The platen consists essentially of a low-friction material, such as aluminum or of a heat-resistant vitreous material. For this specific purpose a borosilicate glass, as for example, the commercially available trademarked Pyrex" would be satisfactory, although understandably other types of material having high resistance to heat and low coeflicients of friction, would quite readily lend themselves to this application.

A resilient plate or guide member 12 is positioned to contact the surface 13 of platen 11 and serve as a supporting surface for the diazo-type material when said materials are transported between guide member 12 and surface 13. Guide member 12 may be formed of fiberglass coated with a surface layer 14 of low-friction polytetrafluoroethylene, known commercially by the trade name Teflon. Although not all surfaces of the guide member 12. need be coated with the Teflon, at least that portion of member 12 contacting surface 13 of platen 11 should be so coated, to thereby provide a relatively frictionless passage for diazo-type materials passing along platen 11 between surfaces 13 and 14.

Preferably, resilient guide member 12 should be positioned with respect to platen 11 so that the Teflon surface 14 exerts a degree of uniform pressure against contacting surface 13 of platen 11. The uniform pressure between surfaces 13 and 14 will assure a constant contact between the diazo-type materials passing through the developer and surface 13 of platen 11.

It also becomes readily apparent that the resilient construction of guide member 12 permits lateral movement of Teflon surface 14 toward and away from surface 13, thereby facilitating the processing of diazo-type materials having different thicknesses and also maintaining the 3 desired compressive force on the materials against platen 11.

Although the guide member 12 has been described as being constituted of an essentially resilient material, such as, for example, fiberglass, it will be obvious to one skilled in the art that a relatively rigid guide member may be utilized, which may be suitably spring-mounted so as to present a resilient surface relative to the surface of platen 11.

Resilient member 12 may be fastened to end frames in a manner quite similar to that employed in attaching platen 11. In planar physical dimensions platen 1-1 and guide member 12 may be substantially identical for reasons to be more fully explained further below.

A materials infeed roller assembly comprising a drive roller 15 and an idler roller 16 is positioned adjacent to and substantially parallel with one edge of platen 11 and guide member 12. The rollers 15 and 16 may be suitably journaled in end frames 10, and rotative motion imparted to drive roller 15 through a prime mover (not shown). Parallel with the infeed roller assembly and adjacent to the opposite edge of the platen 11 and guide member 12 is a materials egress roller assembly constituted of a drive roller 17 and an idler roller 18.

The construction of the egress roller assembly 17, 18 is quite similar to that of infeed roller assembly 15, 16. Thus, idler rollers 16 and 18 may be of resilient construction and positioned in compressive or spring-loaded relationship with their respective drive rollers 15 and 17. This, in effect, will assure that the diazo-type materials fed into the bite between the driver rollers and the idler rollers will be firmly and positively gripped for movement therethrough.

Egress roller assembly 17, 18 is journaled in the end frames 10 in a manner substantially analogous to that of infeed roller assembly 15, 16. Similarly, driver roller 17 may be driven in synchronous rotation with driver roller 15 by the identical prime mover rotating the latter or by other means (not shown).

The platen 11 is heated to within a predetermined temperature range through a heater 19 fastened or bonded to the surface of the platen. The optimum operating temperature of the platen 11 has been found to be in the range of 148 to 160 C. The heater 19 may be essentially of the flexible silicone-molded type covering a substantial portion of the platen surface 11 in order to impart uniform heat thereto. A satisfactory heater may be formed of #32 wire, 180 alloy-resistance wire which has been covered with a silicone rubber-coated glass blanket and subsequently vulcanized by heat and pressure. A feature of this construction is that the heater 19 will rapidly raise the platen 11 temperature to the required operating temperature while using only a relatively small amount of electrical energy input.

In order to maintain the temperature of the platen 11 within the desired operating range, a temperature control 21 or thermostat for the heater 19 is positioned on or near the surface of the platen 11. The thermostat is preferably of the differential-1y expansible type, basically consisting of a closed end copper tube 20 containing a metal rod of a dissimilar material. Operation of the thermostat unit 21 is a function of the difference in expansion rates of the two dissimilar metals. A thermostat of this type will provide close control over the temperature and energy output of the heater 19. Differentially expansible thermostats are widely and commercially available and no further detailed description is required in this regard.

To facilitate retention of the desired heat and temperature range in the platen 11 and developing apparatus a suitable thermal deflector 22, formed of sheet metal, and an insulating material 23 may be placed above the platen 11 and heater 19. A similar thermal deflector 24 and insulating material 25 may be positioned below guide member 12, thereby providing a generally well insulated developer assembly.

In operation, exposed sensitized material is fed into the bight of infeed rollers 15, 16. The material is gripped between the rollers and conveyed between heated platen surface 13 and Teflon coated surface 14 of guide member 12. The edge of platen 11 is bent upwardly while the edge of the guide member 12 slopes downwardly to thereby form a substantially V-shaped groove facilitating the conveyance of the material therebetween.

As the exposed sensitized material passes in sliding contact with the practically frictionless surfaces 13, 14 of platen 11 and guide member 12, the heat of the platen will effect the desired developing process in the material.

When the leading edge of the developed material emerges between surfaces 13 and 14, it will be introduced into the bite of egress rollers 17, 18; gripped therebetween and conveyed out of the developing apparatus into a suitable receptacle or tray.

Preferably, the infeed roller assembly 15, 16 and the egress roller assembly 17, 18 should be driven at synchronous speeds in order to maintain a uniform tension on the diazo-type material as it is conveyed through the developing apparatus. Satisfactory roller and material speeds of up to 10 linear feet per minute may be attained with this developing apparatus.

Referring now to FIG. 2, the embodiment of the apparatus shown therein is basically the same as that in FIG. 1, and accordingly, like components have been given identical reference numerals. Here, however, the platen surface 13 and guide member cover surface 14 are straight, whereas in the embodiment of FIG. 1, they are, respectively, convex and concave. The present embodiment thus eliminates the possible need for straightening the material after it emerges from the space between surfaces 13 and 14.

A further feature of this embodiment is that the heat reflectors and insulating materials have been re-arranged to some extent. This in essence, however, has no material effect on the operation of the developing apparatus.

Referring now to FIG. 3, this embodiment of the apparatus is quite similar to that of FIG. 2, however, the guide member 12 has been replaced by a moving endless conveyor belt 26 moving around rollers 27, 28 and 29 in synchronous motion with rollers 15 and 17. The belt 26 will assist in sliding the material past surface 13 of stationary platen 11. The belt 26 may be constituted of low coefiicient of friction, high temperature-resistant material. It may be of two-ply construction, consisting of fiberglass cloth coated with a silicon rubber compound, the laminations being appropriately wound and vulcanized.

Although the apparatus of each of the embodiments herein described has been shown with a single platen only, it will be readily apparent that by utilizing a plurality of platens and infeed rollers in series, or by increasing the width of the platen, the contact time between the material and platen will increase and thus will provide higher processing speeds.

While particular embodiments of this invention are shown above, it will be understood that the invention is obviously subject to variations and modifications without departing from its broader aspects.

What is claimed is:

1. An improved thermographic developing apparatus including in combination a flat, stationary platen; a resilient support guide member; a roller assembly for conveying thermographically responsive material between said platen and said guide member and heating means adjacent one surface of said platen for heating said platen, the improvement including a resiliently supported guide member positioned to contact a surface of said platen when said thermographically responsive material is not being processed; said roller assembly including infed roller means adapted to convey materials between said platen and said guide member at feed rates up to 10 linear feet per minute; and an egress roller assembly for conveying said thermographic material from the area be 5 tween said platen and said guide member to the exterior of said apparatus, having a drive roller and an idler roller in contact therewith to maintain a uniform force on said infed roller assembly permitting uniform tension on the material conveyed between said platen and said guide member.

References Cited UNITED STATES PATENTS 2,941,573 6/1960 Cassady 34-41 X 3,114,254 12/1963 Rose 34-41 X ..3,115,731 12/1963 Blythe et a1. 156-583 X 3,163,104 12/1964 Lapham 100-93 X RICHARD 6 Hutchinson et a1. 156-583 X Aser et a1. 219-216X Limberger 219-216 Cassano et a1 95-1.7 X Limberger 219-216 Rice 95-89 Aizqwa 100-93 X M. WOOD, Primary Examiner.

US. Cl. X.R. 

